scholarly journals Fusion, fission, and transport control asymmetric inheritance of mitochondria and protein aggregates

2017 ◽  
Vol 216 (8) ◽  
pp. 2481-2498 ◽  
Author(s):  
Stefan Böckler ◽  
Xenia Chelius ◽  
Nadine Hock ◽  
Till Klecker ◽  
Madita Wolter ◽  
...  
Keyword(s):  
Protein Aggregates ◽  
Asymmetric Division ◽  
Cell Organelles ◽  
Mitochondrial Transport ◽  
Daughter Cells ◽  
Transport Control ◽  
Live Cell Microscopy ◽  
Mitochondrial Distribution ◽  
Cell Microscopy

Partitioning of cell organelles and cytoplasmic components determines the fate of daughter cells upon asymmetric division. We studied the role of mitochondria in this process using budding yeast as a model. Anterograde mitochondrial transport is mediated by the myosin motor, Myo2. A genetic screen revealed an unexpected interaction of MYO2 and genes required for mitochondrial fusion. Genetic analyses, live-cell microscopy, and simulations in silico showed that fused mitochondria become critical for inheritance and transport across the bud neck in myo2 mutants. Similarly, fused mitochondria are essential for retention in the mother when bud-directed transport is enforced. Inheritance of a less than critical mitochondrial quantity causes a severe decline of replicative life span of daughter cells. Myo2-dependent mitochondrial distribution also is critical for the capture of heat stress–induced cytosolic protein aggregates and their retention in the mother cell. Together, these data suggest that coordination of mitochondrial transport, fusion, and fission is critical for asymmetric division and rejuvenation of daughter cells.

scholarly journals Direct lysosome-based autophagy of lipid droplets in hepatocytes

2020 ◽  
Vol 117 (51) ◽  
pp. 32443-32452
Author(s):  
Ryan J. Schulze ◽  
Eugene W. Krueger ◽  
Shaun G. Weller ◽  
Katherine M. Johnson ◽  
Carol A. Casey ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Lipid Droplets ◽  
Critical Role ◽  
Specific Protein ◽  
Lipid Homeostasis ◽  
Dynamic Interactions ◽  
Double Membrane ◽  
Live Cell Microscopy ◽  
Cell Microscopy

Hepatocytes metabolize energy-rich cytoplasmic lipid droplets (LDs) in the lysosome-directed process of autophagy. An organelle-selective form of this process (macrolipophagy) results in the engulfment of LDs within double-membrane delimited structures (autophagosomes) before lysosomal fusion. Whether this is an exclusive autophagic mechanism used by hepatocytes to catabolize LDs is unclear. It is also unknown whether lysosomes alone might be sufficient to mediate LD turnover in the absence of an autophagosomal intermediate. We performed live-cell microscopy of hepatocytes to monitor the dynamic interactions between lysosomes and LDs in real-time. We additionally used a fluorescent variant of the LD-specific protein (PLIN2) that exhibits altered fluorescence in response to LD interactions with the lysosome. We find that mammalian lysosomes and LDs undergo interactions during which proteins and lipids can be transferred from LDs directly into lysosomes. Electron microscopy (EM) of primary hepatocytes or hepatocyte-derived cell lines supports the existence of these interactions. It reveals a dramatic process whereby the lipid contents of the LD can be “extruded” directly into the lysosomal lumen under nutrient-limited conditions. Significantly, these interactions are not affected by perturbations to crucial components of the canonical macroautophagy machinery and can occur in the absence of double-membrane lipoautophagosomes. These findings implicate the existence of an autophagic mechanism used by mammalian cells for the direct transfer of LD components into the lysosome for breakdown. This process further emphasizes the critical role of lysosomes in hepatic LD catabolism and provides insights into the mechanisms underlying lipid homeostasis in the liver.

The endocytic adaptor Numb regulates thymus size by modulating pre-TCR signaling during asymmetric division

Blood ◽  
2010 ◽  
Vol 116 (10) ◽  
pp. 1705-1714 ◽  
Author(s):  
Rocio Aguado ◽  
Nadia Martin-Blanco ◽  
Michael Caraballo ◽  
Matilde Canelles
Keyword(s):  
Cell Fate ◽  
Asymmetric Division ◽  
Cell Receptor ◽  
Dominant Negative ◽  
Thymocyte Development ◽  
Tcr Signaling ◽  
Daughter Cells ◽  
Fate Determinants ◽  
Cell Fate Determinants

Abstract Stem cells must proliferate and differentiate to generate the lineages that shape mature organs; understanding these 2 processes and their interaction is one of the central themes in current biomedicine. An intriguing aspect is asymmetric division, by which 2 daughter cells with different fates are generated. Several cell fate determinants participate in asymmetric division, with the endocytic adaptor Numb as the best-known example. Here, we have explored the role of asymmetric division in thymocyte development, visualizing the differential segregation of Numb and pre-TCR in thymic precursors. Analysis of mice where Numb had been inhibited by expressing a dominant negative revealed enhanced pre–T-cell receptor (TCR) signaling and a smaller thymus. Conversely, Numb overexpression resulted in loss of asymmetric division and a larger thymus. The conclusion is that Numb determines the levels of pre-TCR signaling in dividing thymocytes and, ultimately, the size of the pool from which mature T lymphocytes are selected.

scholarly journals Spindle assembly requires complete disassembly of spindle remnants from the previous cell cycle

2012 ◽  
Vol 23 (2) ◽  
pp. 258-267 ◽  
Author(s):  
Jeffrey B. Woodruff ◽  
David G. Drubin ◽  
Georjana Barnes
Keyword(s):  
Spindle Assembly ◽  
Anaphase Promoting Complex ◽  
Daughter Cells ◽  
Microtubule Polymerization ◽  
Conditional Mutant ◽  
Double Mutant Strain ◽  
Spindle Disassembly ◽  
Live Cell Microscopy ◽  
Bipolar Spindles ◽  
Cell Microscopy

Incomplete mitotic spindle disassembly causes lethality in budding yeast. To determine why spindle disassembly is required for cell viability, we used live-cell microscopy to analyze a double mutant strain containing a conditional mutant and a deletion mutant compromised for the kinesin-8 and anaphase-promoting complex-driven spindle-disassembly pathways (td-kip3 and doc1Δ, respectively). Under nonpermissive conditions, spindles in td-kip3 doc1Δ cells could break apart but could not disassemble completely. These cells could exit mitosis and undergo cell division. However, the daughter cells could not assemble functional, bipolar spindles in the ensuing mitosis. During the formation of these dysfunctional spindles, centrosome duplication and separation, as well as recruitment of key midzone-stabilizing proteins all appeared normal, but microtubule polymerization was nevertheless impaired and these spindles often collapsed. Introduction of free tubulin through episomal expression of α- and β-tubulin or introduction of a brief pulse of the microtubule-depolymerizing drug nocodazole allowed spindle assembly in these td-kip3 doc1Δ mutants. Therefore we propose that spindle disassembly is essential for regeneration of the intracellular pool of assembly-competent tubulin required for efficient spindle assembly during subsequent mitoses of daughter cells.

scholarly journals Cooperative 4Pi Excitation and Detection Yields Sevenfold Sharper Optical Sections in Live-Cell Microscopy

2004 ◽  
Vol 87 (6) ◽  
pp. 4146-4152 ◽  
Author(s):  
Hilmar Gugel ◽  
Jörg Bewersdorf ◽  
Stefan Jakobs ◽  
Johann Engelhardt ◽  
Rafael Storz ◽  
...  
Keyword(s):  
Live Cell ◽  
Live Cell Microscopy ◽  
Cell Microscopy

scholarly journals Live-cell microscopy - tips and tools

2009 ◽  
Vol 122 (6) ◽  
pp. 753-767 ◽  
Author(s):  
M. M. Frigault ◽  
J. Lacoste ◽  
J. L. Swift ◽  
C. M. Brown
Keyword(s):  
Live Cell ◽  
Live Cell Microscopy ◽  
Cell Microscopy

Stem cell self-renewal: The role of asymmetric division

2009 ◽  
Vol 36 (5) ◽  
pp. 425-429 ◽  
Author(s):  
V. V. Terskikh ◽  
A. V. Vasil’ev ◽  
E. A. Voroteliak
Keyword(s):  
Stem Cell ◽  
Asymmetric Division ◽  
Self Renewal
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